Many organic compounds are soluble in an organic solvent but insoluble in water. On the other hand, many inorganic reacting agents such as sodium hydroxide are soluble in water but insoluble in an organic solvent. Therefore, even if an attempt is made to cause a reaction of an organic compound in an organic solvent with an inorganic reacting agent in an aqueous solution, because they are not miscible to each other, the reaction takes place only in the interface of the phases contacted to each other; and thus, the reaction rate thereof is extremely slow. Accordingly, in an organic synthesis reaction, the reaction is sometimes carried out by adding a phase-transfer catalyst into the reaction system comprising an organic solvent solution of an organic compound and an aqueous solution of a reacting agent while stirring the resulting mixture (Patent Document 1).
The reaction taking place in the interface of two liquids not miscible to each other can be enhanced in its efficiency by using a microreactor. This is because the mass transfer in the interface takes place efficiently as a result of drastic increase in the contact area per unit volume in this interface (Patent Document 2 and Patent Document 3).
However, the microreactor described in Patent Document 2 and Patent Document 3 is of a so-called static type; therefore, in reality, as the diameter of the micro flow path becomes narrower, the pressure loss thereof is inversely proportional to the fourth power of the diameter of the flow path, indicating that a large liquid-feeding pressure is needed so that obtaining a pump capable of feeding the fluid is practically difficult; and in addition, in the case of the reaction accompanied with separation, the micro flow path is closed up due to the phenomenon that the product clogs the flow path as well as bubbles formed by the reaction. Further, because it is expected that the reaction is basically dependent on the diffusion rate of the molecules, the micro space is not effective and applicable in every reaction; and thus, practically, the reaction needs to be studied with a trial-and-error approach so as to finally select a proper one. All in all, there are many problems with the microreactor of this type.
The issue of up-scaling has been dealt with by increasing the number of the microreactor itself, namely, by numbering-up; however, in reality, possible multiplication number thereof is limited to several tens; and thus, the use thereof is prone to valuable products. Further, the increase in the number of equipment means an increase in absolute number of causes of the troubles; and thus, when a trouble such as clogging actually takes place, it is very difficult to identify the problem such as the spot of the trouble.
In order to solve the problems in production of an organic compound as mentioned above, a microreactor of a forced thin film type is proposed wherein fluids are caused to react in a thin film fluid formed between processing surfaces which are disposed in a position they are faced with each other so as to be able to approach to and separate from each other, at least one of which rotates relative to the other (Patent Document 4).
The invention disclosed in Patent Document 4 relates to a production method of an organic compound in which many examples of organic reactions are described; however, there is no disclosure with regard to a phase-transfer catalysis reaction. Nevertheless, as disclosed in Patent Document 4, uniformity of temperature and uniformity of the reaction in the thin film fluid are also high in the microreactor of a forced thin film type; and thus, if the phase-transfer catalysis reaction is applied to it, it is natural to expect a high reaction yield.
Therefore, inventors of the present application tried to carry out the phase-transfer catalysis reaction by using the microreactor of a forced thin film type disclosed in Patent Document 4; but contrary to the expectation, it was found that a favorable result could not be obtained as the yield thereof was about 50%.